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srcu: Check for consistent per-CPU per-srcu_struct NMI safety 

This commit adds runtime checks to verify that a given srcu_struct uses
consistent NMI-safe (or not) read-side primitives on a per-CPU basis.

Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Paul E. McKenney 2022-09-19 14:03:07 -07:00
parent 2e83b879fb
commit 27120e7d2c
3 changed files with 43 additions and 12 deletions
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12
include/linux/srcu.h
View File

@ -65,14 +65,14 @@ unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
#ifdef CONFIG_NEED_SRCU_NMI_SAFE
int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) __acquires(ssp);
void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) __releases(ssp);
#else
static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
{
return __srcu_read_lock(ssp);
}
static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe)
{
__srcu_read_unlock(ssp, idx);
}
@ -192,7 +192,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp
int retval;
if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
retval = __srcu_read_lock_nmisafe(ssp);
retval = __srcu_read_lock_nmisafe(ssp, true);
else
retval = __srcu_read_lock(ssp);
rcu_lock_acquire(&(ssp)->dep_map);
@ -237,7 +237,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
WARN_ON_ONCE(idx & ~0x1);
rcu_lock_release(&(ssp)->dep_map);
if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
__srcu_read_unlock_nmisafe(ssp, idx);
__srcu_read_unlock_nmisafe(ssp, idx, true);
else
__srcu_read_unlock(ssp, idx);
}

5
include/linux/srcutree.h
View File

@ -25,6 +25,7 @@ struct srcu_data {
/* Read-side state. */
atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */
atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */
int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */
/* Update-side state. */
spinlock_t __private lock ____cacheline_internodealigned_in_smp;
@ -42,6 +43,10 @@ struct srcu_data {
struct srcu_struct *ssp;
};
#define SRCU_NMI_UNKNOWN 0x0
#define SRCU_NMI_NMI_UNSAFE 0x1
#define SRCU_NMI_NMI_SAFE 0x2
/*
* Node in SRCU combining tree, similar in function to rcu_data.
*/

38
kernel/rcu/srcutree.c
View File

@ -626,6 +626,26 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
/*
* Check for consistent NMI safety.
*/
static void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe)
{
int nmi_safe_mask = 1 << nmi_safe;
int old_nmi_safe_mask;
struct srcu_data *sdp;
if (!IS_ENABLED(CONFIG_PROVE_RCU))
return;
sdp = raw_cpu_ptr(ssp->sda);
old_nmi_safe_mask = READ_ONCE(sdp->srcu_nmi_safety);
if (!old_nmi_safe_mask) {
WRITE_ONCE(sdp->srcu_nmi_safety, nmi_safe_mask);
return;
}
WARN_ONCE(old_nmi_safe_mask != nmi_safe_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_nmi_safe_mask, nmi_safe_mask);
}
/*
* Counts the new reader in the appropriate per-CPU element of the
* srcu_struct.
@ -638,6 +658,7 @@ int __srcu_read_lock(struct srcu_struct *ssp)
idx = READ_ONCE(ssp->srcu_idx) & 0x1;
this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter);
smp_mb(); /* B */ /* Avoid leaking the critical section. */
srcu_check_nmi_safety(ssp, false);
return idx;
}
EXPORT_SYMBOL_GPL(__srcu_read_lock);
@ -651,6 +672,7 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
smp_mb(); /* C */ /* Avoid leaking the critical section. */
this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter);
srcu_check_nmi_safety(ssp, false);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@ -661,7 +683,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
* srcu_struct, but in an NMI-safe manner using RMW atomics.
* Returns an index that must be passed to the matching srcu_read_unlock().
*/
int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
{
int idx;
struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
@ -669,6 +691,8 @@ int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
idx = READ_ONCE(ssp->srcu_idx) & 0x1;
atomic_long_inc(&sdp->srcu_lock_count[idx]);
smp_mb__after_atomic(); /* B */ /* Avoid leaking the critical section. */
if (chknmisafe)
srcu_check_nmi_safety(ssp, true);
return idx;
}
EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
@ -678,12 +702,14 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
* element of the srcu_struct. Note that this may well be a different
* CPU than that which was incremented by the corresponding srcu_read_lock().
*/
void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe)
{
struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
smp_mb__before_atomic(); /* C */ /* Avoid leaking the critical section. */
atomic_long_inc(&sdp->srcu_unlock_count[idx]);
if (chknmisafe)
srcu_check_nmi_safety(ssp, true);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock_nmisafe);
@ -1125,7 +1151,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
int ss_state;
check_init_srcu_struct(ssp);
idx = __srcu_read_lock_nmisafe(ssp);
idx = __srcu_read_lock_nmisafe(ssp, false);
ss_state = smp_load_acquire(&ssp->srcu_size_state);
if (ss_state < SRCU_SIZE_WAIT_CALL)
sdp = per_cpu_ptr(ssp->sda, 0);
@ -1158,7 +1184,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
srcu_funnel_gp_start(ssp, sdp, s, do_norm);
else if (needexp)
srcu_funnel_exp_start(ssp, sdp_mynode, s);
__srcu_read_unlock_nmisafe(ssp, idx);
__srcu_read_unlock_nmisafe(ssp, idx, false);
return s;
}
@ -1462,13 +1488,13 @@ void srcu_barrier(struct srcu_struct *ssp)
/* Initial count prevents reaching zero until all CBs are posted. */
atomic_set(&ssp->srcu_barrier_cpu_cnt, 1);
idx = __srcu_read_lock_nmisafe(ssp);
idx = __srcu_read_lock_nmisafe(ssp, false);
if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, 0));
else
for_each_possible_cpu(cpu)
srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu));
__srcu_read_unlock_nmisafe(ssp, idx);
__srcu_read_unlock_nmisafe(ssp, idx, false);
/* Remove the initial count, at which point reaching zero can happen. */
if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt))